We're sorry to hear about your collision with a deer but glad you are unhurt. We have not tested any specific deer repeller devices ourselves, but there are plenty of ultrasonic deer warning whistles available on Amazon and eBay. Most are less than £10 and simply stick on your bumper or grill while the reviews generally seem favourable so it's worth a go. Although the risk of encountering deer is increased in rural areas, the chances of being involved in a collision with one is thankfully relatively low.